The purpose of this pilot study is to develop and evaluate an exposure metric designed for use in a case-control epidemiological investigation of childhood cancer and agricultural chemicals in California. The research design will build upon an existing collaborative effort between the principal investigators to improve the spatial resolution of the California Pesticide Use Reporting database(CPUR). Of the studies in the epidemiologic literature which bear on the possible pesticide/childhood cancer association, most suggest an increased risk. The methods to be employed in achieving the goal include: (1)To use remote sensing and geographic information system (GIS) technology to map crop locations in California in order to link agricultural pesticide use reported in CPUR to crops located near residences used in the case-control study; (2) To evaluate the exposure metric from Specific Aim 1 in terms of (a) integration with more advanced computer models for pesticide transport in the environment, (b) reduction in misclassification of exposure, and (c) transferability across the State of California; and (3) To conduct a pilot epidemiological study using the exposure metric developed by Specific Aim 1.